This application claims the priority of German Application No. 198 05 478.5, filed Feb. 11, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a 3/3-way valve and, more particularly, to a 3/3-way valve with a valve chamber formed in a valve housing, said chamber having a connecting opening for a fluid source and a fluid consumer as well as a relief opening, and with a control member movable in the valve chamber relative to the latter in three control positions, in which positions a maintenance of pressure, an increase of pressure, and a reduction of pressure are produced in the fluid consumer.
With such a fluidic control valve, the control functions ("maintain pressure," "increase pressure," and "reduce pressure") are possible in the three control positions of the valve in a connected fluid consumer. 3/3-way valves of this kind are usually designed as slide valves, for example as lengthwise slide valves, in which a control piston with a plurality of grooves opens and closes the connecting openings alternately in a cylinder bore. All manual, mechanically electrical, and pneumatic actuating modes are possible for actuating and returning the lengthwise slide valve. In designing such slide valves as plate slide valves which, as a rule, are operated only by hand or foot, a rotary motion of the slide is required to switch the valve.
Because of the geometry of the slide and the valve chamber which is usually made in the form of a housing bore, slide valves of this kind require a relatively high manufacturing cost, mainly due to the exact fit of the slide in the housing bore. Due to the geometric shape of the slide and the housing bore, it is very difficult to seal the individual chamber sections off from one another in the three control positions of the control slide.
A hydraulic 2/2-way valve is already known, such as in DD 24 986, in which the valve chamber is divided into two chamber sections by a control piston. The sections are connected with one another by a through bore in the control piston. A supply line from a hydraulic source terminates in one chamber section, and a feed line to a consumer departs from the other section. The connecting openings for the hydraulic source and consumer are arranged so that the control piston in its basic position abuts the end wall of one chamber section, closing the connecting opening to the consumer, and clears this opening after a control stroke, while the connecting opening for the hydraulic source is not controlled. A second piston that is rigidly connected with the control piston seals off this connecting opening to prevent loss by leakage. The fact that the control piston abuts the end wall of the chamber section in the basic position and shuts off the consumer opening at the same time means that no overlap is required when switching the control piston. This is done so that the control stroke of the control piston can be made very small and approximately corresponds to the inside diameter of the connecting opening. This small piston stroke shortens the switching time of the control valve considerably. The preferred area of application of the known 2/2-way valve is hydraulic digital computers.
A known compressed-air valve that constitutes a 4/2-way valve, such as in DE 40 40 797 A1, has a control member designed as a disk with a surrounding sealing ring. The disk extends in a plane that is diagonal with respect to the valve chamber axis and is mounted nonrotatably on a shaft coaxial with the chamber axis. Each two valve connecting openings in the form of radial bores are located on diametrical sides of the valve chamber, and are offset axially with respect to one another in such fashion that each pair of openings terminates in one of the chamber sections of the valve chamber that is separated from one another by the disk. In one control position of the control member, the openings of the pair of openings that terminate in one chamber section are connected with one another, and in a second control position rotated through 180 degrees, each pair of openings located diametrically opposite one another in each chamber section are connected with one another.
The goal of the invention is to improve a 3/3-way valve of the above-mentioned type by reducing its manufacturing costs.
The goal is achieved according to the invention by a 3/3-way valve with a valve chamber formed in a valve housing, said chamber having a connecting opening for a fluid source and a fluid consumer as well as a relief opening, and with a control member movable in the valve chamber relative to the latter in three control positions, in which positions a maintenance of pressure, an increase of pressure, and a reduction of pressure are produced in the fluid consumer. The valve chamber is divided by the control member into two chamber sections delimited thereby, said sections being in a fluid exchange connection with one another. The three openings are arranged relative to one another at certain intervals. The control member in one control position blocks the consumer opening and the relief opening, in another control position covers only the relief opening, and in an additional control position covers only the supply opening.
The 3/3-way valve according to the invention has the advantage that the control piston, despite the three control positions required for 3-way control, divides the valve chamber into only two chamber sections. These two chamber sections are permanently connected with one another. Not only can the control member be designed to be very much more simple from the manufacturing standpoint, but also the sealing off of the control member from the housing bore poses much less of a problem. This is because the control member, in all of the control positions, is only required to cover the valve connection openings, namely only one valve connecting opening in each of two control positions and a total of two valve connecting openings in one control position, and no longer a plurality of chamber sections. In the design of the valve as a lengthwise slide valve, a simple cylindrical displacement piston with a central piston rod for its actuation suffices as the control member. The piston is guided displaceably in a valve chamber in the valve housing designed as a cylindrical bushing. In the design of the valve as a plate valve, the control member is a disk with control segments that fit flat against the end faces of the lid surfaces delimiting the cylindrical valve chamber endwise. In both cases, in successive control positions of the control member, the desired control functions "maintain pressure," "increase pressure," and "reduce pressure" are possible in its actuation direction. High tolerance requirements are not imposed on the manufacture of these valves. The control member can be sealed by sealing rings, which are made for example in the lengthwise slide version of the valve as simple O-rings, which can be placed in an annular groove on the circumference of the piston or in annular grooves in the inside wall of the cylinder bore between the three openings.
Advantageous embodiments of the 3/3-way valve according to the invention are shown and described herein.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.